The present invention generally relates to metal oxide semiconductor field effect transistor (MOSFET) devices, and more specifically, to MOSFET devices with a doped bottom barrier layer.
The MOSFET is a transistor used for amplifying or switching electronic signals. The MOSFET has a source, a drain, and a metal oxide gate electrode. The metal gate is electrically insulated from the main semiconductor n-channel or p-channel by a thin layer of insulating material, for example, silicon dioxide or glass, which makes the input resistance of the MOSFET relatively high. The gate voltage controls whether the path from drain to source is an open circuit (“off”) or a resistive path (“on”).
N-type field effect transistors (NFET) and p-type field effect transistors (PFET) are two types of complementary MOSFETs. The NFET uses electrons as the current carriers and with n-doped source and drain junctions. The PFET uses holes as the current carriers and with p-doped source and drain junctions.
In conventional III-V MOSFET devices, short-channel effects are improved by incorporating a heavily doped p-type bottom barrier layer. The heavily doped p-type bottom barrier layer is often epitaxially grown entirely under the source/drain contact region.